Situated deep in a valley on Ice lies a small forest. The trees are like trees you'll find on any Prime tundra, except they're completely encased in ice and covered by snow. A dark sky hangs over the valley, but a faint light, like starlight, descends from the skies to illuminate the forest. The entire place glows like a magical, crystalline forest lit up by a full moon.

Within Sigil and the planes exist Factions, organizations which adhere to a certain belief, which shapes the multiverse even further to their ideal. Indeed, many call them philosophers with clubs.

They hold many positions in the City of Doors and run many of the services, from the prisons held by the Mercykillers, to the Foundry worked by the Believers of the Source, to the Dustmen operating the Mortuary.

This is a collection of sensations hand selected from the vaults of the Society of Sensation. They reflect a variety of lives and experiences that will enrich any who would choose to consider them.

And without further delay:

Any faction would find clerics useful -- even the Athar have priests of the Great Unknown -- but clerics of particular gods or belief systems will
either be namers only, or divided in their beliefs, unless they
honestly consider their religion and their faction philosophy to meld
into a single spiritual path. More common than such theological balancing acts might simply be those clerics who draw their power from the faction philosophy.

The Anarchist prestige class by Christopher Campbell

The Bleaker prestige class by Christopher Campbell

The Dustman prestige class by Christopher Campbell

The Faithful prestige class by Christopher Campbell

The Godsman prestige classes and affiliation by Christopher Campbell

The Guvner prestige class by Christopher Campbell